Spray foam under cedar shingles

[Andy Engel]

Hi folks. I've got an interesting situation.

Older home, new cedar shingle roof on purlins, open to the attic. The homeowner wants to insulate the roof with spray foam. I love spray foam, but in this case think we need to maintain an air space. Nothing I've found at the Cedar Shingle and Shake Bureau's website suggests otherwise, and I have a call in to them.

Anyone found a good way to handle this? I'm thinking spray foam with either proper vents from eaves to ridge, or creating an air channel with rigid foam and spacers.

Thanks for any input.

Andy

[David Meiland]

The air channel with rigid foam and spacers sounds semi-promising, but is the rigid foam stiff enough to handle the weight of the SPF hanging from it? Don't the SPF manufacturers want their product sprayed against sheathing?

[gzajac]

Andy

I have always been amazed at how much water the cedar and the strapping sucked up during a rainstorm, and didn't leak. I always imagined that the volume of air in the attic held moisture until it had time to dryout naturally.

I love foam, and the hot roof concept, but believe you need to be very careful depending on soffit vent and ridge vent will dry this out quick enough. If it was me I would let someone else test it out on their dime, and report back.

I am sure you will do a great job, probably too good. What happens if the roof starts leaking? Where will the water come out?When will you discover the leak? How will you find it? Is the homeowner a friend?

When I was younger I took a lot of chances, I am not as bold anymore.


Greg in Connecticut

Are you presenting at JLC this year?

[Andy Engel]

Hi Gents.

You've both raised issues that concern me. And maybe this is one of the times foam isn't appropriate. The spray foam guy is really good - he may have a method that's worked before. I just haven't talked with him yet.

Fiberglass? Nooo....

Greg, yes, I'm presenting at JLCLive in Providence. I'd go to that show even if I had to pay - It's the best. I only wish I had time to go to Angelos with Mike Smith and company. Stop by and say hi. Or you can always buy me a beer after the show...

[NW Architect]

Any underlayment under the shingles? If not, definitely NO SPF: it will foam out between the shingles.

If yes, I'd research compatibility between foam and felt

[Dick Seibert]

You guys keep talking about foams, I don't know an AHJ that will allow any foam at this point, first the Rhode Island Station fire, then the Las Vegas high rise fire. There is a very active contingent in the fire protection industry trying to make all foams illegal in buildings, and that includes the so-called fireproof foams like XPS.

The inspector, Denis Larocque, offered an explanation in a previously unreleased state police interview that was made public Wednesday, as were more than 3,000 pages of evidence from the now-resolved criminal case in the Feb. 20, 2003, fire.

In an inspection a few months before the fire, Larocque said he was so focused on an exit door that swung the wrong way that he never saw the foam.

The documents were released in response to requests made to the state attorney general's office by The Associated Press, The Providence Journal and The Boston Globe.

Two months ago, the club owners agreed to plea deals and were sentenced on 100 counts each of involuntary manslaughter for the fire. Michael Derderian was sentenced to serve four years in prison, and his brother, Jeffrey, received community service and probation.

They have maintained they did not know the foam installed in June was flammable.

Also serving four years behind bars is Daniel Biechele, who as tour manager for the rock band Great White ignited a pyrotechnics display that set fire to the foam. The club was immediately consumed with flames and dense, black smoke.

In a transcript of a brief interview with the state police a few days after the fire, Larocque was asked if he noticed during a November 2002 inspection whether there was foam around the stage area.

"No, I did not," he replied, then added that he was focused on an exit door that swung the wrong way and had previously been listed as violating code. He said seeing the door again violating code so surprised him that "I really didn't look anywhere."

A message left for Larocque at the town fire department was not immediately returned.

The club was repeatedly inspected after the brothers told the town they installed soundproofing.*

Here is the recent final settlement, the foam industry has a long way to go if they really do now have fireproof products, but at this point anybody installing foam, or allowing it to be installed is subject to huge damages. I realize that coming from a state that has not only suffered huge damages from wildfires, but the litigation capital of the world, we are probably very sensitive to this issue, but I would either avoid it, or take steps to legally protect yourself, we have cities even banning foam coffee cups and plates around here for being carcinogens, so all it will take is for somebody to come down with cancer in a foam covered home and you *will* be named in a lawsuit, and your insurance company *will* throw money on the table to get out, with all the bad press about foams they would never risk a jury trial. Remember, fireproofing an inflammable product like foam means adding more potentially toxic chemicals to it, if it gets hot it starts emitting toxic gasses, and it's the gasses that maim and kill, much more so than the fire.

*http://cms.firehouse.com/web/online/...tclub/46$52230

[tom struble]

how about adding 1x2 to the sides of the rafters then 3/8 ply then foam to that?

[Andy Engel]

Dick, spray foam is done all the time around here. I don't know a single AHJ who objects, but Connecticut isn't California. It does need to be covered with drywall, but that's usually the only concern.

Tom, I'm thinking you're onto the right answer. Except I'd probably use OSB 'cause it's cheap. And I need to verify the roof venting. Absent that, I'm going to steer away from this entirely.

Again, thanks for your comments and suggestions.

[tayriver]

I'd use the suggestion from Tom Struble, and you can go quick and dirty on the plywood installation given that the foam will seal gaps or cracks in the work. Lots of guys will spray closed cell foam onto cardboard baffles. I can't vouch for that technique, but it's definitely being done.

My local bldg dept's accept Dow's Thermax Polyiso in place of drywall as an ignition barrier, and allows it to remain exposed in attics and crawlspaces. Thermax is >R7/inch. Might be about the same cost as installing and firetaping drywall too, so sort of a no-brainer.

[Dick Seibert]

Connecticut isn't California

But Connecticut is closer to Rhode Island, I'm surprised you to don't have fire marshals screaming about the dangers of foam like we have here.

[Andy Engel]

But Connecticut is closer to Rhode Island, I'm surprised you to don't have fire marshals screaming about the dangers of foam like we have here.

That's true, but like I said, Connecticut ain't California. In fact, I know builders in Rhode Island who use foam all the time. And it's not just spray foam - in the northeast, we use foam-cored SIPs, sheathe with foam, and even make concrete forms out of the stuff.

No material is perfect, and nearly anything used inappropriately can be hazardous. Take water, for example.

[tayriver]

I was speaking with my SPF guy today about something else, and ran this situation by him. He says that in any framed cavity they'll spray foam "onto pretty much anything". He's spraying a closed cell, polyurethane foam. But they spray to cardboard all the time. They'll even do a quick flash over XPS 'quick' owing to the fact that otherwise XPS tends to melt.

[James Eggert]

Dick
The sprayed foams we use here do not support combustion. That is the simple explanation, however, our codes we use here in CT, both the IRC2003 and the IBC2003 have sections which relate as to how these spray "INSULATIONS" should be used.

We all know CA has its own agenda in this world!

PS. I still like you, though!

[Dick Seibert]

Jim:

This isn't a California thing, it's a nationwide movement from the fire protection industry in response to the firefighter deaths and illnesses from inhaling the gasses from burning foams. Making the foams fire resistant isn't really the solution since it's the gasses exhumed by the foam, sure it off-gasses less if it's not burning, but even heating it releases deadly gasses. Probably the banning of foam cups and plates is a California thing like the banning of other plastics, but as you know what starts in California soon travels into other parts of the nation.

I don't see this as an insurmountable problem; after all, they use foam to extinguish fires, in fact putting water on a fire should be totally eliminated, it causes more damage than the fire itself in today's mold liability environment, firefighter's trucks should be equipped with foam and not water, like they have been doing at airports for many years. Whatever chemical they are putting in fire extinguishing foams should be incorporated in all foams, and that goes for foam furnishings as well.

[R Factor]

As I am a foam installer, I had to jump in on this one. I would not install foam of any kind against this roof deck, in this situation. There are just to many unknowns here. I would either spray the ceiling or air seal the ceiling and have either cellulose or blown FG installed.